Objectives: We examined the relationship between a physical activity monitor, which measures physical activities and health behavioural factors, and behavioural changes in 70 first-year university students who consented to participate among 80 students (recovery rate, 87.5%).

Methods: We evaluated Pearson’s correlation coefficients using the Mann-Whitney U-test for changes in health behavioural factors and self-efficacy and performed binomial logistic regression analysis with health behavioural factors and self-efficacy as dependent variables and life improvement effects as explanatory variables.

Results: The analysis revealed a positive correlation among five items of expectations of life improvement, health behavioural factors and self-efficacy. The score of “health behaviour and expectations of life improvement effects” was higher than those of health behavioural factors and self-efficacy. Binomial logistic regression analysis revealed that self-efficacy is related to health behavioural factors, health behaviour and expectations of life improvement effects.

Conclusions: Using the physical activity monitor to confirm behavioural science theory, health behavioural factors, self-efficacy and health behaviour are found to be effective for young adults to motivate themselves to maintain healthy behaviours.